Supranuclear Downgaze Paralysis With Monocular Elevation Palsy

\s=b\A patient with bilateral infarction in the mesodiencephalic region showed impairment of all downward rapid eye movements (including vestibulo-ocular movements) and foveal smooth pursuit (nondis-$ sociated downgaze paralysis) associated with monocular paralysis of elevation (vertical one-and-a-half syndrome). Bell's phenomenon and all types of horizontal eye movements were preserved. The lesions may have affected the efferent tracts of the rostral interstitial nucleus of the medial longitudinal fasciculus bilaterally and the premotor fibers to the contralateral superior rectus subnucleus and ipsilateral inferior oblique subnucleus, either before or after decussation in the posterior commissure. (Arch Neurol. 1989;46:1361-1363) T^he mesodiencephalic region is the critical area in the mediation of vertical gaze. Selective upgaze paraly¬ sis is related to a unilateral lesion lo¬ cated in the posterior commissure, its nuclei, and the adjacent pretectal area.1·2 Selective downgaze palsy oc¬ curs in bilateral lesions affecting the area located caudal, dorsal, and medial to the upper poles of the red nuclei, a region corresponding with the location of the rostral interstitial nucleus of the medial longitudinal fasciculus (rostral iMLF).34 Supranuclear paralysis of vertical gaze can be differentiated clinically from nuclear or postnuclear le¬ sions by preserved Bell's phenomenon and vertical oculocephalic movements in the absence of voluntary saccades and foveal smooth pursuit movements (dissociated downgaze paralysis).5 We have studied a case of nondissociated downgaze palsy associated with paral¬ ysis of monocular elevation, caused by bilateral thalamomesencephalic in¬ farction. This complex type of vertical oculomotor dysfunction, known as ver¬ tical one-and-a-half syndrome, in con¬ trast with the horizontal one-and-ahalf syndrome resulting from lesions affecting the paramedian pontine re¬ ticular formation and the medial lon¬ gitudinal fasciculus,6 has not previ¬ ously been reported to our knowledge. No pathologic studies of vertical oneand-a-half syndrome are available in the literature. We believe the present study provides the first clinical, oculographic, and magnetic resonance im¬ aging documentation of this complex vertical oculomotor syndrome.